1. Field of the Invention
The present invention relates to a liquid ejecting apparatus for ejecting a liquid drop from a nozzle opening of a liquid jet head to an article to be processed.
2. Description of the Related Art
As a typical example of a conventional liquid ejecting apparatus, there is an ink jet recording apparatus having an inkjet recording head for recording images. As other liquid ejecting apparatus, for example, an apparatus having a color material jet head used for manufacturing color filters of liquid crystal displays, an apparatus having an electrode material (conductive paste) jet head used for forming electrodes of organic EL displays and face emission displays (FED), an apparatus having a biological organic substance jet head used for manufacturing biological chips, and an apparatus having a sample jet head as a precise pipette may be cited.
An ink jet recording apparatus as a typical example of the liquid ejecting apparatus has been recently used in many printings including color printings because printing noise is comparatively low and small dots can be produced highly densely.
Such an ink jet recording apparatus generally has an ink jet recording head moving back and forth in the width direction (head scanning direction) of a recording medium (an article to be processed) loaded on a carriage such as recording paper and a feed mechanism for moving a recording medium in the direction (feed direction) perpendicular to the head scanning direction and further has a platen which is arranged opposite to the recording head, supports the recording medium fed by the feed mechanism from the back side, and specifies the position of the recording medium with respect to the recording head.
The ink jet recording apparatus prints by ejecting ink drops onto recording media by the recording head in correspondence with print data. And, the recording head loaded on the carriage can eject ink in various colors, for example, black, yellow, cyan, and magenta, thus not only text printing can be realized by black ink but also full-color printing can be realized by changing the ejection rate of each ink.
When the overall surface of each recording medium is to be printed free of blanks on the edges of the recording medium (so-called four-side edge-free printing) by the ink jet recording apparatus, in consideration of an allowance for displacements of the recording medium and carriage, an area slightly wider than the size of the recording medium is printed.
Namely, in order to make it possible that the surface of the recording medium can be printed free of blanks on the left and right edges (edges in the feed direction) of the recording medium, the scanning range of the recording head during printing can be set wider so as to extend beyond the side edges of the recording medium.
Furthermore, when the surface is to be printed free of blanks on the front and rear edges (edges in the head scanning direction) of the recording medium, at the start time of printing the recording medium, up to an area extending beyond the front edge of the recording medium is designated as an area to be printed and also at the end time of printing the recording medium, up to an area extending beyond the rear edge of the recording medium is designated as an area to be printed.
And, ink drops ejected into the areas beyond the recording medium are absorbed by an absorbent member (sponge, etc.) arranged on the rear side of the recording medium opposite to the recording head.
However, the ink absorbent member is arranged on the rear side of the recording medium away from the same and the distance from the nozzle opening to the ink absorbent member is longer than the distance from the nozzle opening to the recording medium. Therefore, when ink drops are ejected into an area outside the recording medium, the ink drops ejected from the nozzle opening slow down upon receipt of the air resistance and may be misted before reaching the ink absorbent member. Particularly, when the volume (weight) of ink drops is made smaller so as to improve the image quality, the speed reduction degree due to the air resistance is increased and ink drops are apt to be misted.
Further, the inside of the ink jet recording apparatus is an almost enclosed space surrounded by a case, so that when the carriage moves in the head scanning direction, at the same time that air is pushed out by the moved carriage, air flows in the part where the carriage passes through. As a result, forward and downward the carriage in the moving direction, a descending air stream is generated, while backward and downward the carriage, air is flown up and an ascending air stream is generated. FIG. 16 is a drawing showing the flow of wind (air stream) when a carriage 101 having a recording head 100 moves to the left on the paper surface. Further, in FIG. 16, a numeral 102 indicates recording paper.
Further, due to the movement of the carriage 101, not only forward and backward in the moving direction of the carriage 101 but also downward in the left and right directions, an ascending air stream is generated. Further, in FIG. 17, numeral 103 indicates platens for supporting the recording paper 102 from the rear thereof.
Ink drops misted before reaching the ink absorbent member, as shown in FIGS. 16 and 17, splash around on the wind generated due to the movement of the carriage 101 and the majority of ink mist is applied to projections (commonly called diamond ribs) 104 making contact with the rear of the recording paper 102 so as to support the recording paper 102. The diamond ribs 104 always rub against the recording paper 102, thereby is easily charged with static electricity and easily attract ink mist by the attraction force due to the static electricity.
When ink mist is deposited on the diamond ribs 104 like this, the deposited ink mist is applied to the rear of the recording paper 102, thus stripe-shaped strains may be generated on the rear of the recording paper 102. Such stains on the rear of the recording paper 102 cause a problem particularly in printing of both sides and postal card print.